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The Tidal Freshwater Zone

A tidal freshwater marsh along the upper Cape Fear River estuary, near Wilmington, NC

Bull-tongue Arrowhead (Sagittaria lancifolia).  Arrowheads can not survive in salty water.  They are common in the freshwater marshes in the upper reaches of the estuary.

Pickerelweed (Pontedaria cordata) has showy purple flowers that bloom in the early summer.  It is another plant commonly found in North Carolina tidal freshwater marshes.

Soft Rush (Juncus effusus) is a rush, like Black Needlerush (Juncus roemerianus).  But it can not survive in salty water.  While Black Needlerush grows in salt and brackish marshes, Soft Rush is only found in freshwater marshes.  Waterlilies (Nyphae species) are also common in the tidal freshwater zone.

A tidal swamp forest in Brunswick County, NC

Tidal Freshwater Marsh

Tidal freshwater marshes are found in the upper part of estuaries.  This far from the sea, there is little or no salt in the water.  These marshes may be flooded by tides every day or they may only flood every once in a while.   The tides bring nutrients and sediment from the ocean into the marshes.  This makes tidal freshwater marshes very good places for plants to grow.  Tidal freshwater marshes are a lot like salt marshes, but without the salt.  Many more kinds of plants can grow in tidal freshwater marshes because the water is not salty.

The plants that grow in tidal freshwater marshes changes throughout the year.  In the winter, the marsh has only bare mud.  In the spring, fleshy broad-leaved plants such as arrowheads begin to grow.  In the summer, these plants are replaced by grasses and grass-like plants.  Some of the plants found in these marshes are Giant Cordgrass (Spartina cynosuroides), Sawgrass (Cladium jamaicense), Cattails (Typha species), Arrow Arum (Peltandra virginica), Pickerelweed (Pontedaria cordata), and Blue Flag (Iris virginica).

More birds use tidal freshwater marshes for feeding, nesting, and breeding, than any other type of marsh.  Tidal freshwater marshes are important for both freshwater and salt water organisms.  Freshwater fish feed in these marshes.  Many estuarine and marine species use them as nursery habitat .  

Tidal Swamps

Tidal swamps grow around freshwater sounds and along the mouths of both blackwater and brownwater rivers.  They grow far up the estuary, where salt water does not reach.  Tides bring fresh water into and out of the water each day.  Because the trees can not stand salt, major storms like hurricanes can cause a lot of damage.  The trees can usually survive being flooded with salt water every once in a while.  But, if storms bring salt into the swamp too often, it can kill the trees.  Then, the swamp will be replaced by marsh. 

Tidal swamps have many of the same trees as riverine swamps.  Some of the trees that grow in tidal swamps are Bald Cypress (Taxodium distichum), Water tupelo (Nyssa aquatica), and Swamp tupelo (Nyssa biflora). 


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